Secure File Sharing Web App with Expiring Links

Emailing sensitive documents as attachments is still the default in most colleges and small offices — and it is a bad one: attachments live forever in inboxes, get forwarded accidentally, and nobody can revoke them. Expiring-link sharing fixes the core problem by making access temporary by design. This project builds that properly, not as a toy uploader: files are encrypted client-side with AES-256 before they ever reach the server, each share link is a cryptographically signed token carrying its own expiry timestamp, and the server rejects expired or revoked tokens without needing cleanup jobs. Around that core sit the features a real product needs — password-protected links, burn-after-reading, per-link download counters and a full access log showing every download, expiry and failed password attempt.

1. The user drops files into the browser; each file is encrypted locally with a random AES-256 key (WebCrypto API) before any byte leaves the machine.
2. The encrypted blob uploads in chunks with progress tracking; the server stores ciphertext plus metadata (name, size, content type) — never the key or plaintext.
3. On "Create link", the server issues a signed token (HMAC) embedding the file ID, expiry timestamp, password flag and burn flag; the decryption key travels only in the link fragment, which the server never receives.
4. A recipient opening the link gets the ciphertext and decrypts it in their own browser using the fragment key; the server checks the token signature and expiry first.
5. Every access attempt — success, expired token, wrong password — is appended to the link's access log.
6. A scheduled sweeper deletes expired ciphertext; burn-after-reading links delete on first successful download.

Tech stack:

• Node.js, Express
• WebCrypto AES-256-GCM (client-side)
• HMAC-signed URL tokens
• bcrypt (password hashing)
• PostgreSQL (metadata + logs)
• Chunked resumable uploads
• Docker (deployment)
• HTML/CSS/JavaScript UI

• [Client-side encryption] Files are encrypted with AES-256 in the browser before upload — the server stores only ciphertext and never sees plaintext.
• [Expiring share links] 1-hour, 24-hour or 7-day expiries; each link is a signed token with an absolute expiry the server enforces on every request.
• [Password protection] Optional per-link passwords with server-side bcrypt hashing and rate-limited attempts.
• [Burn after reading] Single-download links that delete the file permanently after the first successful retrieval.
• [Access logs] Every download, expiry, failed password attempt and revocation is logged with timestamp and location for the link owner.
• [Instant revocation] Kill any link immediately from the dashboard; in-flight downloads are cut off.
• [Drag-and-drop uploads] Multi-file queue with progress bars, resumable chunked uploads for large files.

• Complete full-stack source code (client + server)
• Client-side encryption and signed-token implementation
• Access-log and revocation dashboard
• Security design document (threat model, key handling, token design)
• Deployment guide (VPS, HTTPS, storage sizing)
• Project report PDF (background, cryptography choices, architecture, testing)
• PPT presentation for final review
• Viva Q&A preparation document (AES-GCM, HMAC tokens, bcrypt, threat model)